Bosentan

INTRODUCTION

Indications

Primary pulmonary hypertension in patients with WHO class III or IV symptoms.

Action

Antagonizes the effects of the neurohormone endothelin by binding to its receptor sites in endothelium and vascular smooth muscle. Therapeutic Effects: Improved exercise capacity and decreased clinical deterioration.

Adverse Reactions/Side Effects

CNS: headache, fatigue. EENT: nasopharyngitis. CV: edema, hypotension, palpitations. GI: HEPATOTOXICITY, dyspepsia. Derm: flushing, pruritus. Hemat: anemia.

PHYSICAL THERAPY IMPLICATIONS

Examination and Evaluation

• Be alert for signs of hepatotoxicity, including anorexia, abdominal pain, severe nausea and vomiting, yellow skin or eyes, fever, sore throat, malaise, weakness, facial edema, lethargy, and unusual bleeding or bruising. Notify physician immediately if these signs occur.

• Assess exercise tolerance to help determine if drug therapy is successful in improving exercise capacity. Document any changes in exercise time, intensity, fatigue, and so forth.

• Assess blood pressure periodically, and compare to normal values (See Appendix F). Report low blood pressure (hypotension), especially if patient experiences dizziness, fatigue, or other symptoms.

• Monitor signs of anemia, including unusual fatigue, shortness of breath with exertion, and bruising. Notify physician immediately if these signs occur.

• Assess peripheral edema using girth measurements, volume displacement, and measurement of pitting edema (See Appendix N). Report increased swelling in feet and ankles or a sudden increase in body weight due to fluid retention.

Interventions

• Implement aerobic exercise and endurance training as tolerated to maintain or improve cardiovascular and pulmonary function.

Patient/Client-Related Instruction

• Instruct patient or family/caregivers to report other troublesome side effects such as severe or prolonged headache, indigestion, palpitations, irritation/inflammation in the nose and pharynx, and skin problems (itching, warmth, redness).

Pharmacokinetics

Absorption: 50% absorbed following oral administration in normal patients.

Distribution: 18 L; does not penetrate erythrocytes.

Protein Binding: >98%.

Metabolism and Excretion: Highly metabolized; one metabolite contributes to pharmacologic activity. Eliminated via biliary excretion; <3% excreted in urine.

Half-life: 5 hr.

Contraindications/Precautions

Contraindicated in: Hypersensitivity; Concurrent use of cyclosporine or glyburide; Moderate-to-severe liver impairment; OB/High risk for fetal harm (malformation, stillbirth) if administered to pregnant women. Pregnancy must be ruled out before start of treatment and reliable contraception used throughout treatment. Hormonal contraceptives (all forms) cannot be the sole form of contraception (see drug-drug interactions). Monthly pregnancy tests for women with child-bearing potential is ...